Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

889
FXUS63 KLOT 091909
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
209 PM CDT Thu Apr 9 2026

.KEY MESSAGES...

- Showers and thunderstorms with locally heavy rainfall tonight.
  Amounts may exceed an inch and a half in some areas,
  particularly across northwestern IL, where new rises on area
  rivers and creeks may result.

- Warmer, but more active weather pattern with periods of
  storms returns late in the weekend through early next week.

- A threat for severe thunderstorms exists Tuesday and Wednesday
  of next week.

&&

.DISCUSSION...
Issued at 209 PM CDT Thu Apr 9 2026

A west-to-east oriented surface boundary has stalled across the
southern CWA (south of I-80) this afternoon. A few isolated
to widely scattered showers and storms may develop in it`s
vicinity this afternoon. In fact, there has already been some
hints at this across western IL. However, limited low-level
moisture is expected to curtail the threat of a higher coverage of
storms through late this afternoon. Accordingly, we expect most
areas will remain dry and mild through the remainder of the day,
with temperatures remaining in the 60s to the low to mid 70s
(warmest south).

As we head into this evening, a strengthening southwesterly low-
level jet will promote increasing moisture advection and
convergence right into the low/mid-level baroclinic zone north of
the stationary front into IA/western IL. This, in addition to the
associated strengthening frontogenetic ageostrophic circulation
will support the increasing coverage of showers this evening,
particularly across northwestern parts of the area (from the west-
northwest Chicago suburbs westward across the Rockford metro
area). There will also be a threat for embedded non-severe
thunderstorms and locally heavy rainfall with this activity given
the strongly forced ascent and rapidly moistening profile
(Precipitable water values up around 1.1"). Given the high soil
moisture and high river levels from previous heavy rain in the
past week, this heavy rain (which could exceed 1.5" in some areas
of northwestern IL) may result in at least some localized hydro
issues. Accordingly, to highlight this potential, we have issued
an ESF (Hydro outlook) north of I-80.

The focus for these showers and storms will gradually sag south-
southeastward with the frontal zone overnight into early Friday
morning. Accordingly, a gradual end in the rain is expected from
north-northwest to south-southeast late tonight through Friday
morning. Thereafter, dry weather is anticipated for the remainder
of the day Friday as a seasonably strong surface high begins to
build in from the northwest. Northerly winds in advance of this
surface high will result in a cooler day across the area on
Friday. As is typical this time of year, onshore north-
northeasterly flow will result in the coolest conditions (in the
low to mid 40s) near the Lake Michigan shore. Conversely, areas
farther inland should warm into the low to mid 50s north, and
closer to 60 far south. However, if cloud cover ends up remaining
more substantial during the afternoon, conditions could end up a
couple of degrees cooler than those currently advertised.

Global models/ensembles remain in good agreement with the upper
level pattern becoming more amplified this weekend as a deep upper
trough and closed low develops over the West Coast and downstream
ridging builds across the eastern CONUS. Locally, the surface
high pressure over the area Friday night will progress eastward
towards New England on Saturday. As this occurs, surface winds
will turn southeasterly during the day. While temperatures will
moderate back into the 60s for areas inland from the northeastern
IL Lake Michigan shore, the persistent onshore wind component
into northeastern IL will keep temperatures there several degrees
cooler Saturday afternoon. Broad warm/moist advection, tapping
low-level moisture from the western Gulf, then ramps up Saturday
night into Sunday downstream of surface low pressure which lifts
from the Plains into the upper Midwest. Accordingly, there will be
some low chances (30-40%) for showers and storms Saturday night
into Sunday amidst milder conditions, though the better chances
for showers and storms look to come later Sunday into Sunday
evening.

Even warmer (70s/80s temps), more humid (dewpoints into the 60s)
and more active weather is expected for at least the first half
of next week. During this period, a series of mid-level short
wave disturbances riding the fast southwest flow downstream of the
western CONUS upper trough look to take aim on our region. Of
particular forecast interest as we head into this emerging pattern
early next week, is the threat for a couple of episodes of severe
weather in our near our general region. This is still several
days away, so questions remain on the finer scale details.
However, in spite of this, there is enough of a larger scale
signal to support the SPC highlighting much of our area in a
threat area for severe thunderstorms next Tuesday and Wednesday.
Stay tuned!

KJB

&&

.AVIATION /18Z TAFS THROUGH 00Z SATURDAY/...
Issued at 1217 PM CDT Thu Apr 9 2026

Generally westerly winds and SCT VFR cigs will prevail through
the afternoon and evening hours. A few gusts in excess of 20 kt
may occur at DPA/MDW/ORD this evening.

After dark, an upper-level wave will propagate into the Great
Lakes atop a northward-moving frontal boundary. Winds will shift
northeasterly and cigs will trend downward through MVFR and into
IFR as showers increase in coverage overnight. There should be
a 2 to 3 hour window at each terminal overnight with steady
rain with prevailing visibility of 2 to 4 miles. A lightning
strike or two cannot be ruled out through the overnight hours,
particularly with westward extent.

While shower coverage will taper toward daybreak, cigs will
take longer to improve upward back into MVFR. Winds should
remain northeasterly at ORD/MDW/GYY while trending northerly at
DPA and northwesterly at RFD toward the end of the TAF period.

Borchardt

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

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